One of the most technically challenging goals in neurophysiology is characterization of interneurons that typically exist in the mammalian brain with a sufficiently low density that there is only a very low probability of a successful intracellular recording. Even when successful, the duration of an intracellular recording from an interneuron can be very short; thus, the limited data from such recordings is particularly valuable. Dr. Helen Scharfman is one of only a few investigators in the world who has successfully developed techniques for recording intracellularly from principal (i.e., projection) neurons and interneurons of the hippocampus simultaneously. Because of the technical difficulties alluded to above, however, there are many instances in which simultaneous recordings are interrupted before electrical stimulation or intracellular filling (with dyes or other markers) can be completed which allow conclusive identification of the functional relation between the neuron pair being investigated. We are working with Dr. Scharfman to investigate the possibility that additional information can be extracted from the data successfully collected and that now is typically not used, e.g., spontaneous membrane potential fluctuations and action potential events that may contain information as to the synaptic connections between the two neurons. Both traditional cross-correlation approaches and analysis of coherence in activity of the neurons pairs is being explored. Dr. Scharfman's work on this project is supported by the NINIDS (to HES).